If they are gray they are polybuylene. How old is teh house? The pipe outside underground is probably blue.

: How do you tell if your indoor dark gray pipes are polybutaline? We just had to have our main incoming water line our vacation home in Colorado (small town) relocated and are wondering if the gray continuous pipe used is safe or could leak. At one joint with the existing copper pipe, there is already a small leak. Someone told us that the pipe is polybutaline but not sure how you tell for sure? Obviously, there is no licensed plumber in our town; so we are at the handy man's mercy! This line also goes outside under our foundation and, we assume, is the same material all the way to the main. What should we do?